package com.lagou.sqlSession;


import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @author lyj
 * @Title: SimpleExecutor
 * @ProjectName lagou_project
 * @Description: TODO
 * @date 2020/5/28 21:59
 */

public class SimpleExecutor implements Executor {

    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //注册驱动，获取数据库连接
        Connection connection = configuration.getDataSource().getConnection();
        //获取sql语句：select * from user where id=#{id} and username=#{username}
        //转换sql：select * from user where id=？ and username=？，同时需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql=getBoundSql(sql);
        //获取预处理对象preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //设置参数
          //获取到了参数的全路径
        String paramenterType = mappedStatement.getParamenterType();
        Class<?> parametertypeClass=getClassType(paramenterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = parametertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }
        //执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<Object>();


        //封装返回结果集
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }

        return (List<E>) objects;
    }

    @Override
    public int insertOne(Configuration configuration, MappedStatement mappedStatement, Object... params)throws Exception{
        //注册驱动，获取数据库连接
        Connection connection = configuration.getDataSource().getConnection();

        //获取sql语句： insert into user (id,username) values(#{id},#{username})
        //转换sql： insert into user (id,username) values(?,?)，同时需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql=getBoundSql(sql);
        //获取预处理对象preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //设置参数
        //获取到了参数的全路径
        String paramenterType = mappedStatement.getParamenterType();
        Class<?> parametertypeClass=getClassType(paramenterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = parametertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }
        //执行sql
        int result= preparedStatement.executeUpdate();
        return result;
    }

    @Override
    public int deleteOne(Configuration configuration, MappedStatement mappedStatement, Object[] params) throws Exception {
        //注册驱动，获取数据库连接
        Connection connection = configuration.getDataSource().getConnection();

        //获取sql语句：  delete from user where id=#{id}
        //转换sql：  delete from user where id=?，同时需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql=getBoundSql(sql);
        //获取预处理对象preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //设置参数,因为只有一个Integer类型的参数
        preparedStatement.setObject(1,params[0]);
        //执行sql
        int result= preparedStatement.executeUpdate();
        return result;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if((parameterType!=null)) {
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作：1.将#{}使用？代替 ，2.解析出#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析工作
        ParameterMappingTokenHandler parameterMappingTokenHandler=new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser=new GenericTokenParser("#{","}",parameterMappingTokenHandler);

        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //从#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql=new BoundSql(parseSql,parameterMappings);

        return boundSql;

    }


    @Override
    public int updateOne(Configuration configuration, MappedStatement mappedStatement, Object[] params) throws Exception{
        //由于代码和insert方法完全相同，所以直接引用insertOne方法即可
       return insertOne(configuration,mappedStatement,params);
    }
}
